Seed-storage-protein loci in RFLP maps of diploid, tetraploid, and hexaploid wheat

Abstract

Linkages between high-and low-molecularweight (M ) glutenin, gliadin and triticin loci in diploid, tetraploid and hexaploid wheats were studied by hybridization of restriction fragments with DNA clones and by SDS-PAGE. In tetraploid and hexaploid wheat, DNA fragments hybridizing with a low-M glutenin clone were mapped at the XGlu-3 locus in the distal region of the maps of chromosome arms 1AS, 1BS, and 1DS. A second locus, designated XGlu-B2, was detected in the middle of the map of chromosome arm 1BS completely linked to the XGli-B3 gliadin locus. The restriction fragments mapped at this locus were shown to co-segregate with B subunits of low-M glutenins in SDS-PAGE in tetraploid wheat, indicating that XGlu-B2 is an active low-M glutenin locus. A new locus hybridizing with the low-M clone was mapped on the long arm of chromosome 7A in diploid wheat. No glutenin protein was found to co-segregate with this new locus. Triticin loci were mapped on chromosome arms 1AS, 1BS, and 1DS. A failure to detect triticin proteins co-segregating with DNA fragments mapped at X¹ri-B1 locus suggests that this locus is not active. No evidence was found for the existence of Gli-A4, and it is concluded that this locus is probably synonymous with Gli-A3. Recombination was observed within the multigene gliadin family mapped at XGli-A1 (1.2 cM). Although these closely linked loci may correspond to the previously named Gli-A1 and Gli-A5 loci, they were temporarily designated XGli-A1.1 and XGli-A1.2 until orthology with Gli-A1 and Gli-A5 is established.

A Novel Chimeric Low-Molecular-Weight Glutenin Subunit Gene From the Wild Relatives of Wheat Aegilops kotschyi and Ae. juvenalis: Evolution at the Glu-3 Loci

“…In wheat, eight chimeric genes resulting from g-gliadins and LMW-GS genes were found, which supposedly resulted from crossing over between the Gli-1 and Glu-3 loci (Nagy et al 2005). However, since Gli-1 and Glu-3 are closely linked and their mapping distance is $100 kb (Spielmeyer et al 2000), homologous recombination and exchange between them are rare although interlocus recombination was observed in different Triticum species (Dubcovsky et al 1997). Furthermore, it is very difficult to produce crossing over between genes at the same locus via homologous recombination.…”

Wheat biotechnology: A minireview

“…The factors that had been instrumental for the use of RFLP in wheat was the limited number of polymorphisms observed among wheat lines and more significantly the availability of aneuploid stocks for the determination of chromosomal location of genes. In wheat, RFLP's have been used to map seed storage protein loci (Dubcovsky et al 1997), loci associated with flour colour (Parker et al 1998), cultivar identification (Vaccino et al 1993), vernalization (Vrn1) and frost resistance gene on chromosome 5A (Galiba et al 1995), intrachromosomal mapping of genes for dwarfing (Rht12) and vernalization (Vrn1) (Korzun et al 1997), resistance to preharvest sprouting (Anderson et al 1993), quantitative trait loci (QTL's) controlling tissue culture response (Tcr) (Ben Amer et al 1997), nematode resistance (Eastwood et al 1994;Williams et al 1996;Lagudah et al 1997), milling yield (Parker et al 1999), resistance to chlorosis induction by Pyrenophora tritici-repentis (Faris et al 1997). RFLP markers are also useful in selection programs for resistance against pests and pathogens, which is otherwise labor and time consuming, and to detect homozygous individuals and have been used for resistance to barley yellow dwarf virus (Crasta et al 2000), resistance to wheat spindle streak mosaic virus (Khan et al 2000), resistance against powdery mildew (Hartl et al 1993;Ma et al 1994;Hartl et al 1995), resistance against leaf rust (Dedryver et al 1996;Autrique et al 1995;Feuillet et al 1995;Schachermayr et al 1995;Schachermayr et al 1994), resistance against cereal cyst nematode (Eastwood et al 1994;Lagudah et al 1997).…”

Comparisons of recombination frequencies in hybrids involving telocentric and bibrachial wheat chromosomes

“…For chromosome 1D, loci Xcdo580 (Anderson et al 1992) and XGlu-D1 (Anderson et al 1989) were used. The Xcdo580 locus is on chromosome arm 1DS (RF with centromere=0.05, Dubcovsky et al 1997), and the XGlu-D1 locus is on chromosome arm 1DL (RF with centromere = 0.18, Dubcovsky et al 1997). Additional RFLP markers outside the centromeric regions (Dubcovsky et al 1996) were analyzed for chromosome 1A and 1D.…”